Weren't microwave ovens invented because someone's chocolate melted in their pocket while operating a radio transmitter? Maybe it's just a lady godiva story since it seems weird that the person wouldn't feel overly hot as well, but maybe.
https://en.wikipedia.org/wiki/Microwave_oven#Discovery
The thing is, you don't need a lot of extra heat to melt a chocolate bar on your pocket. It's perfectly possible that everybody felt hot when working on an active radar, but didn't discuss it or maybe even notice the correlation.
> The first food deliberately cooked with Spencer's microwave oven was popcorn, and the second was an egg, which exploded in the face of one of the experimenters.
They were having a blast I see.